North Korean leader Kim Jong Un uses a pair of binoculars to look at the South's territory from an observation post at the military unit on Jangjae, an islet in the southernmost part of the southwestern sector of the North's border with the South, in March 2013. | AP

A new study spotlighting an “undeclared” North Korean missile base that hosts medium-range weapons capable of striking half of Japan was released Friday amid growing concerns in Tokyo over U.S. President Donald Trump’s acceptance of shorter-range missile tests by Pyongyang.

Located 1,100 km west of Tokyo and 75 km north of the Demilitarized Zone, the Kumchon-ni base “houses a battalion- or regiment-sized unit equipped with Hwasong-9 (Scud-ER) medium-range ballistic missiles (MRBM)” as well as shorter-range Hwasong-6 (Scud C) missiles, the study released Friday by the Center for Strategic and International Studies think tank’s Beyond Parallel project said.

The base is reportedly tasked with strikes against the southern half of Japan during wartime, and, to a lesser degree, South Korea, said the study, which claimed to be “the first comprehensive public report detailing the development, organization and threat posed by the Kumchon-ni missile operating base.”

Scud-ER, or extended-range, missiles can travel roughly 1,000 km, and can deliver a 750-kg warhead — a nuclear-weapon-size payload — to all of South Korea and the southern half of Japan, including Shikoku and a large portion of Honshu, it said.

Such a range would put “many bases used by the U.S. military” within striking distance, according to the report.

It also said that the base could eventually play host to “more recently emerging MRBMs” such as the solid-fueled Pukguksong-2 missile, which North Korean leader Kim Jong Un said in May 2017 could be “rapidly mass-produced.”

Should such a deployment become a reality, “the threat envelope could include all of Japan, including U.S. military bases on Okinawa, and beyond,” the study said.

The report said that as of August, the Kumchon-ni base “is active and being well-maintained by North Korean standards,” adding that continued infrastructure changes at the facilities in recent years “attest to the ongoing importance” of the site to the North Korean leadership.

A United Nations panel report on North Korea released Thursday quoted one member state as saying it had observed the deployment of the Pukguksong-2 to “missile bases close to the northern border,” where liquid-fueled Rodong missiles have also been deployed. The North is estimated to possess 200 to 300 of the medium-range Rodong missiles, which can fly about 1,300 km (800 miles).

The North has in recent months conducted a spate of weapons tests, the most recent on Aug. 24, making for a total of at least 11 apparent ballistic missile launches overseen by Kim this year. The pace comes close to matching the frantic speed of testing in 2017, when Trump and Kim traded insults and threats.

But Trump has brushed off the tests of the short-range weapons, saying “a lot of people are testing those missiles, not just (Kim)” — comments that have sent a worrying message to Washington’s Asian allies.

“We are in the world of missiles, folks, whether you like it or not,” he said recently.

During the breakneck pace of its missile testing in 2017, the North also fired four Scud-ER missiles into the Sea of Japan in March, three of which flew over 1,000 km and landed within 350 km of mainland Japan.

In an unusually overt threat to Tokyo, Pyongyang said at the time that the barrage of missiles was a rehearsal for a strike on U.S. military bases in Japan — a simulation of a type of saturation attack that experts say could defeat missile defenses.

Experts later said that the test-firings were training for striking U.S. Marine Corps Air Station Iwakuni in Yamaguchi Prefecture.